Ray Jackendoff (b. 1945) is an American linguist and cognitive scientist, Seth Merrin Professor Emeritus in Humanities at Tufts University and long associated with its Center for Cognitive Studies. An MIT PhD trained under Chomsky, he spent his career arguing that the language faculty is not a single syntax engine with meaning and sound bolted on, but several equal systems working in parallel. He matters to language teaching only indirectly, yet decisively: his model of how the mind represents language is the scaffolding Susanne Carroll builds her theory of acquisition on.
Two ideas carry the weight. The Parallel Architecture treats phonology, syntax, and meaning as independent generative systems, each with its own primitives and rules of combination, tied together by interface (correspondence) rules that let the mind map sound onto meaning. Representational Modularity (Jackendoff 1987, 1997, 2002) is the cognitive claim behind it: the mind is a set of distinct representational modules, and what looks like understanding a sentence is really a chain of translations across these modules, each handing structured representations to the next. His Conceptual Semantics develops the meaning end of that chain in fully mentalistic terms, treating reference and inference as operations over conceptual structures in the head rather than relations to the world.
Autonomous Induction Theory is, in Carroll's own framing, derived from Representational Modularity. The picture of acquisition it yields follows directly from Jackendoff: because the mind is partitioned into autonomous phonological, morphosyntactic, and conceptual systems joined by correspondence rules, learning a second language is in large part learning new cues to cross-level correspondences, and it is triggered when a parse across those levels fails. The units the learner must acquire live inside these representational systems, which is why Carroll denies they can simply be "noticed" in the environment. Jackendoff supplies the architecture; Carroll supplies the learning mechanism that runs on it.